Elevator safety device.



iATENTED MAY 14, 1907. S

0. R; PRATT. ELEVATOR SAFETY DEVICE.

APPLICATION FILED un..s,19o5.

4 SfiEBTS-SHBBT 1.

. WITNESSES INVENTOB;

' mm N 3273M! @MMMW ATTORNEY.

THE NaRRIs PETERS C0,, WASHINGTON, D, C4

PATBNTED MAY 14', 1907.

No". 853,733. v

' c. PRATT.

. ELEVATOR SAFBTY'DEVIGE.

APPLICATION FILED APR. 3, 1905 4 SHEETS-SHEET a.

' INVENTOII WITNESSES I ATTORNEY TH'E Nckms pznms ca., WASHINGTON, n. c.

PATENTED MAY 14, 1907, v

c. R. PRATT. ELEVATOR SAFETY DEVICE. A PPLIOATIOIIILBD APILS, 1905.

4 SHEETS-SHEET s.

i E I m PATENTBD MAY 14, 1907.

0. R. PRATT. ELEVATOR SAFETY DEVICE.

AP PLIOATION TILED APR 1905.

4 SHEETS SHEET 4.

INVENTOR? 7D ATTORNEY THE uomws PEIERS co. \vasnmaron, u. c.

A w i ,w

WITNESSES- AMM i m BY 1% mmm STATES PATENT OFFICE.

ELEVATOR SAFETY DEVICE.

Specification of Letters Patent.

Patented May 14, 1907.

Application filed April 3, 1905- Serial No. 253,437-

To on whom, it may concern:

Be it known that 1, CHARLES R. PRATT, a citizen of the United States,residing at Montclair, in the county of Essex and State of New Jersey,have invented certain new and useful Improvements in Elevator SafetyDevices; and I do hereby declare the following to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same, referencebeing had to the accompanying drawings, and to letters of referencemarked thereon, which form a part of this specification.

This invention relates to safety devices for elevators, and moreparticularly to such safety devices as have jaws located on the car andwhich are adapted in case of accident to grip rails or the like arrangedvertically or longitudinally of the hoist-way.

The objects of the invention are to employ a differential screw foractuating the gripping jaws; to thus secure longitudinal movement of thescrew shaft as a whole; to enable the rope drum to be mounted directlyupon the said screw shaft and thus partake of its said mption; to thusavoid angular deflection of the rope leading to said drum as it winds orunwinds and enable an idler' sheave to be placed close to the drum toautomatically insure that the differential screw shall act by the fullpitch of one of its ends until the gripping jaws come in contact withthe rails and then close said jaws upon the rails bythe differentialaction of its two ends; to thus secure a rapid movement of the grippingjaws up to or against the rails, so that no time will be lost in gettingthem into gripping relation after the car begins to fall; to con 'trolsuch change of action by the act of engagement of the gripping jaws withthe rails; to thus regulate the power applied to the jaws by thenecessity for such power or the work which is to be done; to provideupon the screw shaft detent means for ordinarily preventing the saidshaft from rotating, and to obtain other advantages and results, some ofwhich wi ll be hereinafter referred to in connection with thedescription of the working arts. p The invention consists in theimproved safety device for elevators, and in the arrangements andcombinations of parts of the same, all substantially as will behereinafter set forth and finally embraced in the clauses of the claims.

Referring to the accompanying drawing, in which like letters ofreference indicate corresponding parts in each of the several figures,Figure 1 is a side elevation of an elevator car and its safety deviceattachments complete; Fig. 2 is a rear elevation of the safety devicemechanism at the bottom of the car; Fig. 3 is a view looking upward frombeneath the car and showing one end portion of the safety mechanism,partly in central longitudinal section; Fig. 4 is a continuation of Fig.3 showing the drum end of the said mechanism, also partly in section;Fig. 5 isa detail view of a pair of the gripping jaws in side elevation;Fig. 6 isa detail plan of certain pawls, and Fig. 7 is a section of thesame on line ac, Fig. 6.

In said drawings, 2 indicates an elevator car of. any well-knownconstruction adapted to move between rails arranged longitudinally ofthe hoistway at opposite sides thereof, the rails 3, 3, shown in thedrawings being rigid T-rails each having its rib or stem portion 4, nextto the car. I

Upon the car, preferably at its bottom, are arranged means forautomatically gri ping the said ribs 4, of the rails 3, in case 0accident, so as to bring the car to a gradual stop. These gripping meansare supported upon the bottom of the car by depending brackets 5, 5,having their lower ends braced by a cross rod 6, extending therebetween.Upon the said ends of the brackets 5, are pivoted opposing quadrangularor bell-crank levers 7, 7, adapted at their jaws 8, to bite against theopposite sides of the rib 4, of the T-rail, and having their other faces9, projecting substantially at right angles on opposite sides of thebrackets and their connecting rod 6. Furthermore, upon each end of thesaid rod 6, is mounted a sleeve 10, or 100, adapted to slide on the rodand having at its outer end sideextensions 11, 11, (or 101, 101) adaptedto engage the said levers 7, 7, and force them against the rail 3.

The rod 6, carries upon itself intermediate of its ends and of thesleeves 10, 100, just described, a'hollow shaft 12, which has at itsopposite ends threads of the same kind or diential screw is provided.One end of this hollow shaft, as 13, receives a correspondingly threadednut 14, which is bolted to the sleeve 100. The other end 15, of the saidshaft also receives a correspondingly threaded nut 16, which nuttelescopically enters therection but differing in pitch, so that adifier- ITO 'tremity of the same.

adjacent end of the sleeve 10, and has an annular rib or flange 17, tobear against the ex- The inner end 18, of the nut 16, is then providedwith spring controlled pawls 19, adapted to normally lie in pockets orrecesses 20, of the hollow shaft 12.

A rope drum 21, is fixed upon the said hollow shaft 12, and said drumhas oppositely wound upon itself and anchored thereto, the ends 22, 23,of a governor rope 24, which ends pass outward over an idler sheave 25,upon the edge of the elevator car 2, one extending upward over agovernor sheave 26, and the other downward over the tension sheave 27,and the two meeting to form a closed loop of rope. Under normalconditions, the drum 21, is held from turning by means of spring pawls28, upon the nut 14, and which engage pockets 29, in the outer surfaceof the hollow shaft. In this relation of parts, the rope 24, runs idlyover the governor and tension sheaves 26, 27. If, however, an accidentoccurs so that the car starts to drop and the governor sheave 26,rotates at a speed above the normal, centrifugal weights 30, on saidsheave fly outward and trip a latch 31, to release the same and permit amovable jaw 32, to clamp the rope 24, against a cooperating fixed jaw33. Obviously this stops movement of the rope 2 1, with respect to thegovernor and tension sheaves, and the drum 21, begins to turn, one endof the rope unwinding therefrom and the other end winding upon the drum.When the drum thus begins to turn, the pawls 28, are forced out of theirseats and ride upon the outside of the hollow shaft.

When in case of an accident the hollow shaft 12, thus turns, obviouslythe nut 16, will be held to the shaft by means of its pawls 19, and willturn with the said shaft loosely in the end of the adjacent sleeve 10,there being no pressure upon the jaws to retard the sleeve at thismoment. This insures that the screw threads at that end of said shaftare idle and the full effect of the opposite threaded end 13, of theshaft is utilized to throw the gripping jaws 7, 7, against the rails 3,3. In other words, when the safety device comes into action, thedifferential screw feature does not at first operate an d the jaws 7,are thus quickly carried into contact with the rails 3. When suchcontact is effected however, the pressure of the jaws creates an endthrust of the sleeve 10, against the annular flange 17, of the nut 16,and causes a friction which overcomes that of the pawls 19, in theirpockets. Said pawls are therefore forced out of their seats, and thehollow shaft begins to turn in the nut 16, said nut becoming stationarywith respect to the sleeve 10. The differential screw feature istherefore now brought into play and the aws at the opposite sides of theelevator car are forced into intimate relation to the rails graduallyand with such pressln". as may be desired.

Upon releasing or reversing the hollow shaft 12, the nut 16, remainsstatiomiry with respect to the sleeve 10, until the friction betweensaid nut and the sleeve relaxes sufficiently to let the nut turn withthe shaft. To insure that this shall not happen until the pawls 19, havereached their pockets, l er ate additional friction between the nut 16,and sleeve 10, by means of a ring 31, slidably mounted upon bolts 35,which project from the end of the sleeve outside the flange 1 7, andwhich ring is pressed by springs 36, against the opposite side of saidflange from the sleeve 10.

The pawls 19, (and 28) may obviously be of any suitable and well-knownconstruction, but preferably each of the pawls is pivoted to lugs 37,upon the nut and curved part way around the same as shown. T he free end33, of each pawl is held by a spring 39, to the pivot of the other pawl,and intermediate of its ends the pawl has a projection adapted to extendthrough the wall of the nut into the pockets of the hollow shaft, andwhich may be either integral with the pawl bod as at 40, in Fig. 4, orseparably secured thereto as at 41, in Fig. 3.

It will be understood that the term rails as used herein refers to andis intended to include not only the T-rails shown, but also any knownform of guide rails, the tension strips shown in my co-temporaneousapplication filed March 27, 1905, Serial No. 252,150, or any othersupport; adapted to be frictionallyengaged by means on the ear, thegripping jaws being any such means as just mentioned which will engagecot'iperating rails and can be operated by my differential screwconstruction and, the term differential screw is employed to designate ashaft having at different longitudinal portions of itself threads of thesame kind or direction but of different pitch.

By using the differential screw which .l. have shown, it will be noted,first, that the time occupied by the gripping jaws in engaging theirrails may be regulated by the differ ence in pitch between the twothreaded portions of the screw shaft, and thus the governor-rope drumcan be mounted directly upon the said shaft without the intervention ofgearing such as shown in my prior application, Serial No. 252,150, filedMarch 27. 1905; and second, that longitudinal movement of the screwshaft as a whole, (and therefore of the drum). is secured, with respectto the elevator car, in operating the gripping devices. The first ofthese points requires the use of the idler sheaves 25, Fig. 1, at theedge of the car, but the second point insures that by a propercalculation of the pitch of the threads on the screw shaft, the drumshall move just enough as its rope ends Having thus described theinvention, wh at I claim as new is 1. In an elevator safety'device, thecombination with hoistway rails, of sets of friction members adapted toengage one each of said rails, a shaft having upon differentlongitudinal portions of itself exterior threads of the same kind ordirection but of different pitch, means engaging one of said threadedportions and being'non-rotatably connected to the adjacent set offriction members, similar means engaging the other threaded portion ofthe shaft and rotatably engaging its adjacent set of friction members,and means for automatically turning said shaft upon falling of the car.

. 2. In a safety device for elevators, the combination with hoistwayrails, of friction members adapted to engage said rails, a shaft havingupon different longitudinal portions of itself exterior threads of thesame kind or direction but of different pitch, nuts upon said threadedportions of the shaft, means adapted to non-rotatably transmit motionfrom one of said nuts to its adjacent,

friction member and means for rotatably transmitting motion from theother nut to its friction member, and means automatically operated bythe falling of the car to turn said shaft.

3. In a safety device for elevators, the combination with hoistwayrails, of friction members adapted to engage said rails, a shaft havingdifferentially threaded portions, nuts upon said shaft, means adapted totransmit motion from said nuts to the friction members, and meansadapted to be automatically operated by falling of the car to rotatesaid shaft.

4. In a safety device for elevators, the combination with fixed hoistwayrails, of brackets adapted to depend from a car, a rod extendingbetweensaid brackets, a hollow differential screw shaft upon said rod,nuts upon said shaft, friction members adapted. to be operated by saidnuts to engage the hoist way rails, and means adapted to beautomatically operated by falling of the car to rotate said shaft.

5. In an. elevator safety device, the combination with hoistway rails,of sets of friction members adapted to engage one each of said rails, ashaft having upon opposite end portions of itself threads of the samekind or direction but of different pitch, non-rotatable means engagingone of said threaded portions and transmitting its longitudinal motionto one set of friction members, and other rotatable means having africtional engagement with the shaft to turn therewith and with theadjacent friction members to impart longitudinal movement thereto.

6. In an elevator safetydevice, hoistway rails, friction members adaptedto grip said rails, a shaft having upon different longitudinal portionsof itself exterior threads of the same kind or direction but ofdifferent pitch, means for transmitting motion from said threaded shaftportions to the friction members, and a governor rope drum mounteddirectly on the shaft and having rope grooves of substantially the samepitch as one of the said threaded portions of the shaft.

7. In an elevator safety device, the combination with hoistway rails, ofsets of friction members adapted to engage one each of said rails, ashaft having upon different longitudinal portions of itself exteriorthreads of the same kind or direction but of different pitch, meansengaging one of said threaded portions and being non-rotatably connectedto the ad j acent set of friction members, similar means engaging theother threaded portion of the shaft and rotatably engaging its adjacentset of friction members, and a governor-rope drum mounted directly onthe shaft and hav ing rope grooves of substantially the same pitch asthe threaded shaft-portion whose said engaging means are non-rotatable.

8. In an elevator safety device, hoistway rails, gripping jaws adaptedto engage said rails, a differential screw for operating said jaws, anda governor-rope drum mounted directly upon said screw shaft. I

9. In an elevator safety device, hoistway rails, gripping jaws adaptedto engage said rails, a differential screw for operating said jaws, anda governor-rope drum mounted upon said shaft andhaving peripheral ropegrooves of substantially the same pitch as one of the threaded portionsof the screw.

10. In an elevator safety device, hoistway rails, gripping jaws adaptedto engage said rails, a differential screw, nuts upon said screw one ofwhich is made fast to its adjacent gripping jaws and the other of whichhas a frictional connection to its adjacent gripping j aws, and agovernor-rope drum on said shaft having rope grooves of substantiallythe same pitch as the threaded screw portion which has the said nut madefast to the gripping jaws.

11. In an elevator safety device, hoistway rails, gripping jaws adaptedto be mounted on a car and engage said rails, 'a differential screw andnuts for operating said jaws, and means for causing one of said nuts toeither turn with the screw or be stationary with respect thereto asdesired.

12. In an elevator safety device, hoistway rails, gripping jaws adaptedto engage said IIO rails, a' differential screw and nuts for operatingsaid jaws, means for imparting motion to the screw with respect to oneof the nuts, and other means adapted to be operated as a result of suchmotion to cause the other nut to either turn with the screw or bestationary with respect thereto as desired.

13. In an elevator safety device, the combination with rails for theopposite sides of the hoistway, of opposite gripping jaws adapted to bemounted on a car and engage said rails, an intermediate differentialscrew, a nut on one end of said screw fixed against rotation with thescrew and adapted to transmit its longitudinal motion to the adjacentjaws, and a second nut on the other end which may either turn with thescrew or remain as to rotation independent of such turn ing.

14. In an elevator safety device, the combination with rails for theopposite sides of the hoistway, of opposite gripping jaws adapted to bemounted on a car and engage said rails, an intermediate differentialscrew, a nut on one end of said screw fixed against rotation with thescrew and adapted to transmit its longitudinal motion to. the adjacentjaws, and a second nut on the other end adapted to frictionally transmitits longitudinal motion to its adjacent gripping jaws.

15. In an elevator safety device, hoistway rails, friction membersadapted to engage said rails, a shaft having differentially threadedportions adapted to operate said friction members, detent pawlsprojecting from a non-rotary support and adapted to engage the saidshaft to normally prevent its turning, a governor-rope drum fast on saidshaft, and a governor.

1.6. In an elevator safety device, the combination with hoistway rails,of members adapted to engage said rails, a shaft having upon differentlongitudinal portions of itself exterior threads of the same kind ordirection but of different pitch, and means upon each of said threadedportions connecting the same with its adjacent gripping member, one

of said means engaging its gripping member frictionally and beingadapted to remain stationary with respect thereto or to turn with theshaft according to the relative friction of said. parts.

17. In an elevator safety device, the combination with hoistway rails,of gripping members adapted to engage said rails, a shaft having upondifferent longitudinal portions of itself exterior threads of the samekind or direction but of different pitch, and nuts upon said threadedportions adapted to engage the gripping members, respectively, one ofsaid nuts engaging its adjacent gripping member frictionally and beingadapted to remain stationary with respect thereto or to turn with theshaft according to the relative friction of said parts.

18. In an elevator safety device, the combination with hoistway rails,of gripping members adapted to engage said rails, a shaft having upondifferent longitudinal portions of itself exterior threads of the samekind or direction but of different pitch, means engaging one of saidtlll:ltl((l portions and being held against rotation with the shaft, andother means engaging the other thremhal portion and being free to eitherturn with the shaft or remain imhepeudent of it as to rotation, bothsaid means transmitting longitudinal motion to the gripping members.

19. In a safety device for elevators, the combination with hoistwayrails, of gripping jaws adapted to be mounted on the ear aml engage saidrails, a differential screw adapted to act by one threaded portion aloneto rapidly advance the gripping jaws toward the said rails and by thejoint effect of both threaded portions to force the gripping jaws intoengagement with the rails, and means for operating said screw.

20. In an elevator safetydeviee, hoistway rails, gripping jaws adaptedto engage said rails, an intermediate threaded shaft to operate saidjaws, two nuts mounted on said shaft, means adapted to secure relativerotation of the shaft whereby longitudinal motion is transmitted to thejaws, and means for causing one of the nuts to turn with the shaft andto I'Oll'litlll stationary as to rotation at different sta es of action.

21. In a safety device for elevators, the combination with lmistwayrails and jaws adapted to grip said rails, of a differential screwbetween said jaws, a nut on one end of said screw fixed againstrotationand adapted to transmit longitudinal motion to tl i adjacent jaws, and asecond nut on the other end rotatable with the screw and adapted totransmit its longitudinal motion to the adjacent jaws through africtional thrust bearing.

22. In a safety device for elevators, the combination with hoistwayrails aml jaws adapted to grip said rails, of a differential screwbetween said jaws, a nut on one end of said screw fixed againstrotation, and a second nut on the other end adapted either to turn withthe screw or remain independent of it as to rotation, both said nutstransmitting their longitudinal motion to the gripping aws.

23. In a safety device for elevators, the combination of a car, hoistwayrails, gripping jaws mounted on the air and adapted to engage saidrails, a differential screw to operate said gripping jaws, a windingrope drum mounted on said screw, and idler sheaves on the car, wherebythe longitudinal axial motion of said screw and drum pays the rope onsaid drum to and, from said idler sheaves without angular dell ction inthe l Fad of the rope.

In an elevator safety device, hoistway lOC llC

rails, gripping jaws adapted to engage said rails, an intermediatethreaded shaft to operate said jaws, two nuts mounted on said shaft,means adapted to secure relative rotation of the shaft wherebylongitudinal motion is transmitted to the jaws, and frictional means forcausing one of the nuts to turn with the shaft and to remain stationaryas to rotation at different stages of the action.

25. In an elevator safety device, hoistway rails, gripping jaws adaptedto engage said rails, an lntermediate differential screw to operate saidjaws, means for rotating said screw, and two nuts 011 said screw adapted15 to engage said aws, respectively, one of said nuts engaging itsadjacent jaw frictionally and being adapted to remain stationarytherewith or to turn with the screw according to the relative frictionof said parts.

In testimony,that I claim the foregoing, I have hereunto set my handthis first day of April 1905.

CHARLES R. PRATT.

Witnesses:

RUSSELL M. EVERETT, M. V. DOYLE.

